1. Field of the Invention
This invention relates to a process of producing fine graphic fiber and particularly to a process of selectively generating graphite fiber at a desired position on a substrate.
2. Disclosure of the Prior Art
Very fine cylindrical graphite fiber having around a 10.sup.-9 m diameter which is generally called carbon nano-tube, is characterized having a feature of wound sheets of graphite nets like a concentric column. Therefore, regarding a feature of electric conductivity, the graphite fiber is predicted to have a broadly extended feature from that of metal to that of semiconductor which is originated in the minute structural difference of it, and accordingly, the newly developed applications are expected.
The following two described techniques are known conventional methods for producing graphite fiber. That is, a process of heat treating with high temperature the fibrous product prepared by spinning an organic compound, and a process of growing fibrous product by chemical vapor deposition using an iron catalyst. Further, recently, a process of generating fibers by arc discharge using carbon electrode has been reported. However, in the heat treating method of spun organic compound fibers it is difficult to control the structure of carbon material and it is therefore difficult to obtain a product having good crystallization. On the other hand, referring to the process which uses iron catalyst, it is reported that a fiber having a structure in which the surface of graphite crystal is wound to form a concentric column can be obtained.
Consequently, among the conventional processes for producing graphite fiber, a process using iron catalyst and a process using arc discharge can be selected to produce the so called graphite nano-tube having the structure feature of wound sheets of graphite crystal nets like a concentric column. The process using iron catalyst is explained as follows. An organo metal compound starting material vapor which includes iron, e.g. ferrocene (dicyclopentadienyl iron) is used as the starting material to generate fine iron particles by chemical vapor deposition and produce the graphite fiber by using the iron particles as a catalyst in a reaction vessel. This process must be carried out in the temperature of higher than 1000.degree. C. to generate graphite fibers. The graphite fibers are generated at any location and on any wall surface of the reaction vessel. It is difficult to limit the location on which graphite fiber is generated to any specified location in the reactor. In the case of the process using arc discharge method, graphite fiber is generated on cathode alone like a lump. It is necessary to use a special apparatus for arc discharge, and even using the arc discharge process, it is difficult to generate fiber on a desired position.